PROGRESS-AMS: Coronary Stenting With Magnesium-Alloy Absorbable Metal Stent

Luis Gruberg, MD, FACC

Disclosures

July 20, 2006

Editorial Collaboration

Medscape &

"There is little doubt that in combination with a controlled drug-eluting design and a reabsorbable polymer, the use of an absorbable stent will likely become a valuable tool in the future."

Presenter: Raimund Erbel, MD (University Essen, Essen, Germany)

Coronary artery stent implantation provides excellent vessel wall scaffolding, prevents coronary artery dissection, blocks elastic recoil, and reduces restenosis rates. Nevertheless, stent placement is associated with some drawbacks. Namely, it is a foreign body that permanently resides inside the coronary artery; it also limits further revascularization, reduces vasomotion, and has limited use in children.

To overcome some of these limitations, researchers developed the Absorbable Metal Stent (AMS, Biotronik, Berlin, Germany). The alloy stent is made of 93% magnesium and 7% rare-earth metals. It induces rapid endothelialization, has low thrombogenicity, and a degradation time of 2-3 months. Magnesium was chosen because it is an essential mineral in the body (the body requires approximately 350 mg/day) and the stent is made of < 4.5 mg of magnesium. The alloy also has calcium antagonist and antiarrhythmic properties and, of importance, is not associated with any adverse allergic reactions.

The PROGRESS-AMS[1] study was a prospective, multicenter, consecutive, nonrandomized first-in-man study designed to evaluate the clinical feasibility of the AMS for the treatment of a single de novo lesion in a native coronary artery.

Study Design

Patients were treated in standard fashion with aspirin, clopidogrel (300-mg loading dose and 75 mg maintenance for at least 6 months), periprocedural heparin, and glycoprotein IIb/IIIa inhibition at the physician's discretion. Angiographic follow-up was performed at 4 months.

Primary Endpoint

Rate of major adverse cardiac events (MACE), defined as cardiac death, nonfatal myocardial infarction (MI), and ischemia-driven target lesion revascularization (TLR) < 30% at 4-month follow-up.

Inclusion Criteria
  • > 18 years

  • Ischemia (stable or unstable angina, or a positive stress test)

  • Single de novo lesion in a native coronary artery

  • Reference diameter between 3.0 and 3.5 mm

  • Lesion length < 15 mm

  • Normal myocardial enzymes

Results

A total of 63 patients were enrolled in the study. Device success rate and procedural success rate were both 100%. Baseline clinical characteristics are shown in Table 1.

Table 1. PROGRESS-AMS: Baseline Clinical and Angiographic Characteristics
AMS
(N = 63)
Age (yrs) 60
Diabetes (%) 17
Insulin-treated diabetes (%) 5
Hypercholesterolemia (%) 61
Hypertension (%) 56
Smoking (%) 47
Target vessel
Left anterior descending artery (%) 35
Left circumflex (%) 29
Right coronary artery (%) 37

From baseline to 4-month follow-up, reference vessel diameter decreased and minimal lumen diameter increased (Table 2). Late loss at 4 months was relatively high (1.09 ± 0.51 mm), yielding a 38% rate of ischemia-driven TLR. There was no incidence of cardiac death or nonfatal MI, and there were no reported cases of stent thrombosis at follow-up. Driven entirely by the high rate of TLR, overall MACE (primary endpoint) was 23.8%, which met the study's primary endpoint -- MACE < 30%.

Table 2. PROGRESS-AMS: Angiographic Outcomes
Preprocedural 4-Month Follow-up
Reference vessel diameter (mm) 2.76 ± 0.47 2.66 ± 0.46
Minimal lumen diameter (mm) 1.05 ± 0.38 1.37 ± 0.52
Conclusions
  1. PROGRESS-AMS met the primary endpoint, with high technical and procedural success.

  2. There were no cases of stent thrombosis.

  3. Intravascular ultrasound detected degradation at 4 months.

  4. TLR success rates are comparable to those reported with the use of bare metal stents.

Viewpoint

Although the results of PROGRESS-AMS are somewhat disappointing due to the high rate of late loss and, in turn, an increased need for revascularization, the results nonetheless demonstrate the feasibility and biocompatibility of a totally new concept to treat de novo lesions. The fact that the stent could be delivered successfully and that it provided the necessary scaffolding for the procedure is encouraging. There is little doubt that in combination with a controlled drug-eluting design and a reabsorbable polymer, the use of an absorbable stent will likely become a valuable tool in the future.

Reference
  1. Erbel R, Bonnier JJ, Koolen C, et al, on behalf of the PROGRESS-I Investigators group. Coronary results of the first absorbable metal stent: The PROGRESS-I trial. Program and abstracts from the Innovation in Intervention: i2 Summit 2006, March 11-14, 2006, Atlanta, Georgia. Abstract 2405-9.

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